Process of producing drawn articles



May 5, 1953 Filed April 2, 1949 R. J. MGKAY PROCESS OF PRODUCING DRAWN ARTICLES 2v SHEETS- SHEET 1 HTTR/VEY May 5,- 1953 R. J. MCKAY 2,637,686

PROCESS OF PRODUCING DRAWN ARTICLES Filed April 2, 1949 2 SHEETS-SHEET 2 I l I as pm750 naz/Ris s55 Maw /wcwEL Ness ml /fv 100 110 120 130 140 150 150 170 19D 200 210 220 Pif? Patented May 5, y19553 UNITED vSTATES TNT @iTFlCE PROCESS OF PRODUCING DRAWN ARTICLES Robert .l. McKay, .Basking-Ridge, N. J., assigner to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware Application April 2, 1949, Serial No. 85,167

(Cl. 20d-33) aluminum, has'been that theplating has caused "a lowering of ductility so that the ability to shape by coldfdrawing orstamping-has been seriously and detrimentally reduced. vItfhas been appreciated in the art that such characteristics as good heat conductivity, lightness in Weight, good resistance to denting and other deformation, pleasinig appearance and resistance to undesirable corrosive attacksby foodstuis are all desirable in i.cooking utensils. It has `also `been recognized 4"that all'o` these desirable characteristics were not present in utensils ofthe prior art.

`Whileutensils have been made both 'from the 'severalsolid metals and'alloys mentioned as Well .as combinations of these in the form of laminations,'no practical vmethod has heretofore been "found of Yproducing a laminated metal using alitern'ating layers of rolled and electrodeposited metals which is suiciently strong and ductile to stand the severe deep drawing operation necessary to the manufacture of cooking utensils. yFormer experience Withtheiplating of nickel or other metals on afductile base metal, such as :a

'I aluminum, hasbeen'that the plating has caused a lowering o'I" ductility so thatthe ability to shape bypolcl rolling and stamping has been seriously r`and1detrimentally reduced.

il have discovered that a cooking utensil or other 'article vpossessing all oi the aforesaid desirablecharacteristics is obtained when such an .articleor utensil is cold drawn or pressed from a laminated structure fcomprising a foundation .layer of aluminum and an overlyinglayer iirmly L bonded'tothe'foundation layer and 'consisting of electr'od'epo'sited nickel oi suflicient'thickness to substantially `equal or at Vleastclosely approach 'the strength of the vfoundation layer, with or "Without an-additional'layer of chromium electroi 1 -deposited on said nickel layer and firmly bonded thereto.

' "Itis an'object ofthe presentinvention to provide ailaminated structure adaptable for severe V'cold v drawing operations "and comprising a found dation. layer of aluminum and one or more composite surface layers of corrosion-resisting metals such as nickel and chromium, which are free from constituents such as copper or iron which 'might contaminate foods.

Another object oi the present invention is to provide a cooking utensil having good heat conductivity in a direction parallel to the surface thereof and having a bright and easily cleaned cooking surface.

'A further object of the present invention is the production of cooking utensils in Which the cooking surface is highly resistant to the corrosive action of food products.

It is also Within the contemplation of the present invention to provide an economical, durable, cooking utensil which is light in Weight, which is easy to handle and which is also resistant to deformation, denting and the like.

YIt is another object of the invention to provide a severely drawn composite .metal article, such as a cooking utensil, formed 'from a laminated structure comprising a foundation layer of aluminum and an overlying layer firmly bonded to the foundation layer and consisting of electrodeposited nickel of sufficient thickness to substantially equal the strength of the lfoundation layer with or Without an additional layer of chromium electrodeposited on the nickel layer.

The foregoing and other objects and advantages oi the invention will become apparentfrom the following description taken in conjunction with the accompanying drawings, in Which:

Fig. l is a graphical representation showing the effect of the nickel plate thickness on the ten- Sile strength of the 'composite structure comprising an aluminum base and a nickel plate;

Fig. 2 is a graphical representation of the effect on the Erichsen cup depth of the thickness of an electrodeposited nickel layer on an aluminum foundation layer in a composite product; and

Fig. 3 represents graphically the relationship between Erichsen cup depth tensile strength oi' composite products made of BSO aluminum with various thicknesses of nickel plate.

Generally speaking, the invention contemplates `the provision oi a cold drawn, laminated structure, such as a cooking utensil, which is constituted ci a foundation layer of aluminum and a suriace layer or layers of nickel or nickel and chromium. The surface layer or layers are preierably electrodeposited on the foundation layer and are firmly bonded thereto. The nickel layer is preferably more than .G02 inch vthick and is preferably about one-tenth or more of the thickness of the aluminum foundation layer.

In its broad aspect, the invention contemplates the production of a composite product or laminated structure suitable for cold drawing and comprising a foundation layer of aluminum or other heat-conductive metal, a layer of nickel electrodeposited on said heat-conductive layer and rmly bonded thereto and having a thickness of about one-tenth the thickness of said foundation layer, and a layer of chromium electrodeposited on said nickel layer and rmly bonded thereto and having a thickness of about one-tenth the thickness of the nickel layer. Both plane surfaces of the foundation layer may be provided with the nickel and chromium layers and the chromium layer may be deposited before or after the drawing of the foundation metalnickel structure.

I have found that composite sheets comprising a foundation sheet of aluminum having firmly bonded to the surface or surfaces thereof a layer or plate of electrodeposited nickel of suflicient thickness to possess about the same tensile strength and ductility as the foundation layer and having suiicient adhesion to the aluminum sheet that it is not separated therefrom when the composite structure is subjected to deep drawing operations, are particularly adapted for use in the manufacture of cooking utensils.

In obtaining the results designated by the charts illustrated in Figs. 1 and 2, the nickel layer or plate was electrodeposited on an aluminum foundation layer or sheet of about .020 inch thickness after first preparing the surface of the alumil num layer in the manner described in detail hereinafter. The effect of the nickel plate thickness on the tensile strength is plotted in Fig. 1 for the composite structure or product as plated, as annealed and as calculated. It is seen that the tensile strength of the composite product increases gradually with the nickel thickness. At a thickness of about .003 inch nickel plate, the tensile strength of the original aluminum sheet is nearly doubled. In other words, the strength of the nickel layer or plate is about equal to that of the aluminum sheet. It is to be noted in this graph that the highest values are obtained for the composite sheet in the as-plated condition although the results for the as-plated and annealed composite products generally parallel the calculated strengths.

On referring to Fig. 2, it will be noted that the Erichsen cup depth values decrease somewhat precipitously to a minimum in the initial stages :f

of electrodeposition of the nickel plate, and then reverse to an abrupt upward turn and increase when the deposit attains a thickness of about .0005 inch. The increase in depth value nally attains a level nearly as high as the original sheet when the thickness exceeds about .003 inch. This occurs at approximately the point where the tensile strength of deposited nickel plate equals that of the aluminum base. The chart also shows that somewhat higher but generally parallel results are obtained when the composite aluminumnickel structure or product is annealed for about minutes at about '750 F. The abrupt upward turn occurs at a somewhat lesser thickness for the nickel layer in the annealed composite structure. It is to be particularly noted from the graphs shown in Fig. 2 that the increases in Erichsen cup depth values are obtained to the same degree in the composite structure asplated as are obtained in the composite structure as annealed, although values are slightly higher in the annealed structure.

Fig. 3 further illustrates the relationship between Erichsen cup depth and tensile strength of composite products made of an aluminum sheet and a nickel plate by plotting the Values of depth and strength in terms of per-centages in the same graph. The tensile strength and the Erichsen cup depth values are expressed as percentages of the respective values for unplated aluminum and it is seen that when the tensile strength reaches about 200% the ductility has returned nearly to its original value or In a preferred embodiment, the laminated structure consists of a central layer of rolled sheet aluminum of about .020 to about .040 thickness, an electrodeposited layer of nickel of about .003 to about .004 thickness firmly bonded to both of the plane surfaces of the foundation aluminum layer, and a surface layer of electrodeposited chromium of about .0002 to about .0003 thickness firmly bonded to the nickel surfaces. Alternatively, the nickel-chromium layers may be applied to only one surface of the aluminum foundation layer, thus providing a laminated aluminum-nickel-chromium structure having one exposed surface of chromium and the other exposed surface of aluminum.

It is an essential feature of the present invention, however, that the laminated structure shall be made up of at least one layer of electrodeposted nickel rmly bonded to the surface of a heat-conductive foundation layer, preferably aluminum, and that this layer (or layers) of nickel shall be of sufficient thickness to approximate the strength of the aluminum foundation layer.

The general method of procedure for producing a suitable laminated structure is as follows:

The aluminum foundation layer is thoroughly cleaned, the method of cleaning depending on the type of dirt to be removed. Thus cleaning may be done by any of the well known methods such as vapor-degreasing, alkali cleaner or acid cleaner, for example, nitric acid. After cleaning, the

aluminum sheet is thoroughly rinsed in water and is then dipped in a caustic soda solution for etching. A 5% caustic soda solution at about F. in which the aluminum sheet is etched for about ten seconds has been found to give very satisfactory results. After etching, the aluminum sheet is again thoroughly rinsed in water and ls dipped in concentrated nitric acid at room temperature for about ten seconds for additional cleaning action. The aluminum sheet -is then anodically treated for about 10 to l5 minutes in 35% to 50% phosphoric acid at about '70 F.-90 F. under continuous agitation to build up an oxide film on the surface of the sheet of a nature to improve adhesion of the plating metal. A voltage of about 10 to about 23 volts is used and an arnperage of about 12 amperes per square foot. The aluminum sheet is again thoroughly rinsed in water and is provided with a layer of electrodeposited nickel on each of its plane surfaces.

The plating bath used may be any conventional bath which will deposit a firmly adhering layer of nickel on the prepared aluminum foundation layer, for example, a chloride bath of a Watts bath. The current densties used, however, are critical. The starting current density must be about 10amperes per square foot and this current density is preferably maintained for about 30 seconds. The current density is then gradually in creased until it reaches about 60 amperes per 5 fsqua-refoot after about oneminute. .Plating is "continued vat this latter rate until the .electrodeposited nickel layer 'attains Da thickness of about -threerto four'thousandths of an inch (.003" to .004) then rinsed in Water and dried and is then polished and buied. The buffed sheet is then provided with anelectrodeposited layer vof chromium :on the vnickel surfaces. The chromium plate may be Aelectrodeposited by any well known method v.which is preferably continued until the chromium layer attains a thickness of about .0002. The I.multi-layer, `aluminumenickel-chromium sheet is then annealed at about '750 Eto 800 F. for about AI5Jminutes to 2 hours,'depending on'the original temper ofthe aluminum foundation sheet.

When blanks of suitable contour and dimensionsrare cut, stamped,or otherwise obtained from fcomposite laminated sheets or vproducts prepared in-the manner described heretofore, such blanks may be subjected tocold drawing operations such -las those commonly used in preparing cooking vrutensilsiifithout separation occurring between the aluminum foundation layer vand the electrode- 'posited nickel layer 'or between the electr-odeposited nickeland chromium layers.

Theresults'shown in Figs. 1 and 2 are shown `inl tabulated form in Tables l and 2 in comparison `with results of breaking load tests on l inch wide 'strips of the laminated sheet, the aluminum layer and the nickel layer. The data shown in Table l were obtained from Aannealed laminated strips while data shown in Table 2 were obtained on laminated strips `as plated and 'without subse- The nickel-plated, aluminum sheet is s "quentannea'ling. Tt will be noted'from-thesediglures that the :breaking load forthenickel layers,

num foundation layer when the plated nickel layer. is .003 inch thick. It is also to be particularly noted that the ultimate strength of the laminated sheet, the breaking load required and Vthe Erichsen cup depths continue to increase proportionately as the thickness of thenickel layer is increased. Thus, although the invention in its preferred embodiment contemplates the drawing of a composite sheet having a foundation layer of alum: num Aand an electrodeposited layer of nickel on the foundation layer with each of said'layers being of approximately the thickness thereof desired in the final product, it will be apparent that a laminated sheet in which the aluminum foundation layer and the electrodeposited nickel layer are each of thicknesses considerably greater than those desired in the finished article may be used, the laminated sheet being first rolled to the desired thickness before the drawing operations.

TABLE 1 Ultimate strength of laminated sheet compared with actual breaking load on 1" wide strip of laminated sheet aluminum layer amt nichel layer [Laminations compared with Fricli sen ductility of laminated sheets. `Aluminum thickness .025", SSO, annealed after plating] .Actual lreaking Load on Ult. Strength l WKS Sm? Erichscn 'Thickneiss of Ni uwer minftgd Cup .iny ooo inc eet, s. Depth Lam. Al `sli per bq' m' Sheet, Layer, Layer, Inches Lbs. Lbs. Lbs.

0 0 thousandths l5, 700 314 314 0 0 .B4 0 l thousandti. 16, 300 329 v314 15 15 0.5 thousandths 19, 800 416 314 '102 kv25 1.0 thousandths 22,000 484 314 -170 27 2 0 thousandths 25, 400 610 314 286 29 3 0 thousandths 29, 200 '759 314 445 :30 5.0 thousandtha 31, 200 036 314 622 .'33 10.0'th0usandths 38,300 j 1,149 314 835 .37

'TABLE 2 '[Larninations versus Erichsen ductility of laminated sheets. Aluminum thickness 53", 3SO, no annealing] Actual rlreaking :Load ou Ult. Strength 1 me Smp Erichsen Thickmss of Ni lLayer Laminated Cup in mno inc 1 ,Si eet, libs. e Y T- Depth por sq. in. Ller Lfer Inchesy Lbs. Lbs. Lbs.

0:0 thousandths 15,200 315' :sie o :33 0.1 thousaudil^s 10, l400 32 316 v16 14 0.5 thousandths 2l, 700 156 316 140 14 1.0 thousaudths" 23, 000 500 316 190 24 2.0 thousandths.- f 200 620 316 313i .25 3.0 tnousandths 30,100 784 316 46S i 28 5.0'th0usandthSQ. 33,700 l, 022 v316 706 .30 .10.0 thousandths 3B, 800 .1, 552 315 1, 236 34 As a more specific illustration of the present invention. reference is made to the following examples:

EXAMPLE I A conventional side handle sauce pan was made by the following procedure using the novel composite or laminated product described herein.

Sheets of aluminum alloy, known as 3S, 42" long, 29 wide and .020l thick were cleaned in a vapor degreaser and rinsed in water. The cleaned sheets were etched in a 5% caustic soda solution at 150 F. for about 10 seconds and were again rinsed in water. The etched sheets were then dipped in concentrated nitric acid, followed by rinsing in water. The sheets were then treated as an anode in a 40 Twaddell phosphoric acid solution at a temperature of 80 F. for 12 minutes and at a current density of l2 amperes per square foot. The sheets were again rinsed in water and were treated as a cathode in a low pH Watts type nickel plating bath at amperes per square foot for 30 seconds, the ampereage then being gradually increased to 50 amperes per square foot during the succeeding 30 seconds and the nickel plating was continued at 50 amperes per square foot until the thickness of the nickel plate on each side of the aluminum alloy sheet was about .003. The sheets were then rinsed and dried and were buffed to a high iinish. The bufied plates were then immersed as cathodes in a chromium plating bath of approximately the following compositions:

250 grams per liter chromic acid 2.5 grams per liter sulphate radical The current density used for the chromium plating in the aforesaid bath was about 108 amperes per square foot and was maintained for about 45 minutes or until a plate of chromium about .0002 thick was deposited. The plated sheet, after rinsing and drying, was heat treated in an electric furnace at about '750 F. for 30 minutes and was cooled in the atmosphere. Six circles were cut from the heat-treated sheet and these circles were cold drawn in a single operation to hollow vessels about 7" in diameter and 4%" deep. The vessels were trimmed to a smooth edge which was turned to a roll edge bead. The wrinkles were then spun out on a spinning disc, the vessel was washed and polished to a satin finish, and a stainless steel handle was secured to each vessel with stainless steel rivets.

EXAMPLE II In this example the aluminum alloy sheets of the same composition and dimensions as in Example I were subjected to cleaning and nickel plating procedures identical to that of Example I, but all polishing, heat treating, and chromium plating as described in Example I were omitted. The sheets after being nickel plated were dried and four discs or circles 131,/2 inches in diameter were blanked out and cold drawn to 7 inches diameter and 41/4 inches deep. The drawn shapes were then trimmed, the edges beaded, the wrinkles spun out and they were then polished and buiied to a high mirror finish. They were then cleaned and chromium plated under the conditions described in Example I, using an electrodeposited layer of chromium .0002 inch thick, and a stainless steel handle attached as in Example I.

It will be apparent to those skilled in the art that the general procedures as given in Examples I and II could be followed using discs of the aluminum alloy as the starting material thus eliminating the production of plated scrap. Manyother variations in the foregoing procedure may be made without departing from the spirit of the present invention. Sheets may be produced at a heavier gauge and thereafter rolled to the desired thickness. Polishing and buing may be omitted until after the drawing is completed. All heat treating may be omitted until after the first draw and then included before nal drawing and the annealing may be done either before or after plating with chromium. Also, the chromium plate may be applied after drawing and polishing.

While the present invention is defined with reference to the relation between the tensile strength of the different layers as an important controlling factor in obtaining the desired results it will be understood that the important improvements obtained are not necessarily the result of the tensile strength alone but are obtained in combination with other inherent properties of the metals employed including that of properly related degree of ductility. Also while it is believed that the improved results of the present invention are related largely to the combination of tensile strength and ductility of the specific metals employed there are perhaps other and unrecognized properties inherent in the specic metals and relative thicknesses as employed which contribute advantageously to the successful deep drawing operations.

Although the present invention has been decribed in conjunction with preferred embodiments, it is to be understood that variations and modifications may be resorted to, as one skilled in the art will readily understand. Thus the invention contemplates the use of other metals of high heat conductivity for the foundation metal or other metals of high corrosion resistance for the exposed surfaces of the multi-layer article.

I claim:

1. A process for producing severely drawn articles of composite metal having high heat conductivity and non-corrosive properties which process consists of cleaning and etching a foundation layer sheet of a metal selected from the group consisting of aluminum and high aluminum alloys and having a thickness of from about .020 inch to about .040 inch, dipping said etched sheet in a concentrated nitric acid followed by rinsing in water, anodically treating said dipped sheet in a 35 %-50% phosphoric acid solution at a temperature of about 80 F. with a current Y density of about 12 amperes per square foot for a period of about ten to fifteen minutes, electrodepositing a layer of nickel on the plane surfaces of said foundation layer sheet and controlling the electrodeposition to produce a thickness of the nickel layer of from about .003 inch to about .004 inch and wherein the thickness of the nickel plating is 10% to 15% the thickness of the foundation layer whereby the tensile strength of the composite foundation metal-nickel sheet is approximately double that of the tensile strength of said foundation layer, electrodepositing a layer of chromium of about .0002 inch to about .0003 inch on the exposed surfaces of said nickel layer, heat treating the composite sheet at a temperature of about 750 F. to about 800 F. for from fteen to thirty minutes and deep drawing articles from the sheet so produced.

2. A process for producing severely drawn articles of laminated metal sheet having high heat conductivity and non-corrosive properties which process consists of cleaning and etching a foundation layer sheet of aluminum and having a thickness of from about .020 inch to about .040 inch, dipping said etched sheet in a concentrated nitric acid followed by rinsing in Water, anodically treating said dipped sheet in a 35%-50% phosphoric acid solution at a temperature of about 70 F. to 80 F. under continuous agitation with a current density of about 12 amperes per square foot and voltage of from 10 to 23 Volts for a periocl of about ten to fifteen minutes, electrodepositing a layer of nickel on the plane surfaces of said foundation layer sheet and controlling the electrodeposition to produce a thickness of the nickel layer from about .003 inch to about .004 inch by treating the foundation sheet as a cath ode in a, 10W pH Watts-type nickel plating bath at 10 amperes per square foot for about thirty seconds, increasing the amperage gradually to and continuing at 50 amperes per square foot until a thickness of nickel plating is obtained which is 10% to 15% the thickness of the foundation layer whereby the tensile strength of the composite foundation metal-nickel sheet is approximately double that of the tensile strength of said foundation layer, electrodepositing a layer of chromium of about .0002 inch to about .0003 inch on the exposed surfaces of said nickel layer, heat treating the composite sheet at a temperature of about 750 F. to about 800 F. for from fifteen to thirty minutes and deep drawing articles from the sheet so produced.

ROBERT J. MCKAY.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Electroplating Aluminum, published by Aluminum Co. of America, 1930, Pittsburgh, Pa., pp. 16, 24, 25, 26. 

1. A PROCESS FOR PRODUCING SEVERELY DRAWN ARTICLES OF COMPOSITE METAL HAVING HIGH HEAT CONDUCTIVITY AND NON-CORROSIVE PROPERTIES WHICH PROCESS CONSISTS OF CLEANING AND ETCHING A FOUNDATION LAYER SHEET OF A METAL SELECTED FROM THE GROUP CONSISTING OF ALUMINUM AND HIGH ALUMINUM ALLOYS AND HAVING A THICKNESS OF FROM ABOUT .020 INCH TO ABOUT .040 INCH, DIPPING SAID ETCHED SHEET IN A CONCENTRATED NITRIC ACID FOLLOWED BY RINSING IN WATER, ANODICALLY TREATING SAID DIPPED SHEET IN A 35%-50% PHOSPHORIC ACID SOLUTION AT A TEMPERATURE OF ABOUT 80* F. WITH A CURRENT DENSITY OF ABOUT 12 AMPERES PER SQUARE FOOT FOR A PERIOD OF ABOUT TEN TO FIFTEEN MINUTES, ELECTRODEPOSITING A LAYER OF NICKEL ON THE PLANE SURFACES OF SAID FOUNDATION LAYER SHEET AND CONTROLLING THE ELECTRODEPOSITION TO PRODUCE A THICKNESS OF THE NICKEL LAYER OF FROM ABOUT .003 INCH TO ABOUT .004 INCH AND WHEREIN THE THICKNESS OF THE NICKEL PLATING IS 10% TO 15% THE THICKNESS OF THE FOUNDATION LAYER WHEREBY THE TENSILE STRENGTH OF THE 